1. https://www.instructables.com/id/Two-Part-Silicone-Casting/ 2. https://en.wikipedia.org/wiki/Mastering_(audio)
Here's an argument with citations that the term "master" in the git context does indeed come from the master/slave terminology:
https://mail.gnome.org/archives/desktop-devel-list/2019-May/...
That depends on the time scale you are considering.
I'm don't think it's a necessary change, but I also don't think it's a harmful change.
If the Git cli tool still initializes a new repo to 'master', I'm not going to go out of my way to rename it before I push to GitHub.
I haven't seen any discussion around changing the Git cli tool.
That's not the only sense of the word "master". There are several, but the one used in git's case is that of a copy or instance from which all other copies are made.